The present invention describes a method for performing surgery on the beating heart by coordinating movement of a moving support for the hands of the surgeon and/or the surgeon""s tools in synchrony with the sensed movement of a surgical area on the heart surface
The coronary arteries are very narrow blood vessels (less than 3 mm in diameter) that transport nutrient-rich blood to the heart muscle. Coronary artery disease is caused by the accumulation of materials on their inner walls, causing them to further narrow and reducing the blood flow to some parts of the heart muscle. A complete obstruction causes the tissue to die and the heart to go into cardiac arrest.
There are three main methods for treatment of narrowed coronary arteries. The only method that does not involve surgery is drug therapy, which can improve blood flow and reduce accumulation of materials on the coronary walls. A first interventional method, called angioplasty, employs a catheter that is placed inside the narrowed artery to widen the blood vessel. A second and most drastic interventional method is called coronary artery bypass grafting surgery (CABG).
CABG surgery is a major surgical procedure that involves general anesthesia. Of all coronary artery disease treatments it is the most effective for relief of angina and has been proven to prolong patient survival. The goal of the operation is to provide a new channel for the blood to reach the dying tissue. This new channel is a blood vessel taken from the patient""s own body, generally a piece of vein from the leg or the arm, or an artery from the chest wall. One end of this vessel is grafted to the aorta and the other end is grafted to the coronary artery downstream from the obstruction. When the blood vessel used is an artery from the chest wall, it is grafted directly to the coronary artery. In most cases the patient is put on cardiopulmonary bypass, which allows the heart to be stopped while the circulation and the heart and lung machine performs filtration of the blood. However, there are several damaging effects that arise due to the use of the heart and lung machine. These include: anemia, red blood cell aggregation, gaseous and particulate emboli, hemolysis (red blood cell damage), localized ischemia, among others. The need for stopping the heart arises from the need to obtain a stable suturing area because the suturing process is a complex procedure that involves high skill and accuracy.
Coronary arteries are located on the surface of the heart, therefore during CABG surgery there is no need to open any of the heart chambers. One technical requirement to perform CABG is to have a bloodless anastomotic field, which in the case of surgery on the beating heart can be achieved by a temporary coronary occlusion. Since the only reason for stopping the heart is for stabilization purposes, if there is a way of performing the grafts while the heart is in motion, the heart can itself perform the circulation and filtration of the blood. This eliminates the damaging effects of the cardiopulmonary bypass.
Several approaches have been proposed to perform CABG surgery on the beating heart. All of them consist of stabilizing the heart tissue that surrounds the surgical site without causing significant damage. Systems have been developed that consist of a horseshoe shaped apparatus that presses down on the heart surface to immobilize the area around the coronary artery where the suturing is to take place (see Guidant Access MV stabilizer Set, Guidant Corporation, http://www.guidant.com/products/surgery/access.htm and Gu Y J, Mariani M A, van Oeveren W, Grandjean J G, Boonstra P W. xe2x80x9cReduction of the inflammatory response in patients undergoing minimally invasive coronary artery bypass graftingxe2x80x9d, Annals of Thoracic Surgery 1998; 65:420-4). Since these devices work by pressure, the force that they exert has to be large enough so that the apparatus is in contact with the surface even when the heart is fully contracted. This presents the disadvantage of exerting stresses on the heart that can damage the tissue. Another disadvantage of such devices is that they can only be used to suture on the top surface of the heart. Furthermore, there is a considerable amount of time required to adjust the position of the stabilizing device on the surface of the heart.
Other approaches developed consist of using suction instead of pressure to stabilize the tissue. The disadvantage of such methods is that the stresses that are exerted on the tissue may be high even when used for short periods of time (Cornelius Borst, xe2x80x9cCoronary Artery Bypass Grafting without Cardiopulmonary Bypass and without interruption of Native Coronary Flow using a novel Anastomosis Site Restraining Device (xe2x80x9cOctopusxe2x80x9d), xe2x80x9cJournal of American College of Cardiology, vol. 27, no.6, pp. 1356-64, May, 1996.), and T. Gilhuly, S. E. Salcudean, K. Ashe, S. Lichtenstein and P. D. Lawrence, xe2x80x9cHeart Stabilizer and Surgical Arm Design for Cardiac Surgeryxe2x80x9d, 6 pages, 1998 IEEE International Conference on Robotics and Automation, Leuven, Belgium, May 1998).
Other recently developed systems (see, for example, the Zeus system developed by Computer Motion Inc. or the DaVinci system developed by Intuitive Surgical Inc.) use several interactive robotic arms to position the endoscope and to manipulate the surgical instruments. The surgeon views the surgical site while seated at an ergonomically enhanced console, from where he or she controls the motion of the instruments and the position of the endoscope. Such systems could, in principle, be modified so that the surgeon controls the motion of the robotic arms relative to a selected surgical site, with the robotic arms automatically tracking the motion of the surgical site. For this approach to be effective, the robotic arms have to be able to move fast enough to accurately track the motion of the surgical site. Therefore, two or three arms, each with 4-6 degrees of freedom, would have to move fast enough and accurately enough to track the surgical site. This poses numerous technical challenges. Therefore, the use of robots might still require that the heart be stopped by means of cardiopulmonary bypass.
U.S. Pat. No. 5,871,017 by Mayer discloses a moving hand support that is moved in synchrony with the heart to significantly reduce the relative motion between the heart and the coronary anastomosis site. This system employs a pacer that controls the beating of the heart and also controls the platform movement. The motion of the platform is produced by a cam, shaped so that the pattern of the oscillation follows the heart motion. In the system described in this patent the relative displacement between the moving platform (and, implicitly, the surgeon""s instruments) and the surgical site can be significant, even if the heart motion is synchronized to the hand support by means of a pacer. In fact, it is likely that if the relative motion between the surgical site on the heart and the moving platform is significant, the teachings of this invention cannot be used effectively. Furthermore, cam mechanisms are suggested in U.S. Pat. No. 5,871,017 in order to track the motion of the heart. In fact, whether paced or not, the motion of the coronaries on the heart has been documented to be three dimensional and highly variable, and thus cannot be approximated well by a cam motion.
It is an object of the present invention to provide a method and apparatus that enables virtual stabilization of the heart tissue without damaging forces exerted on it to allow coronary artery bypass grafting surgery to be performed without the use of the cardiopulmonary bypass and without damaging the heart tissue.
Broadly the present invention relates to a method for performing surgery comprising sensing the movement of a selected point and controlling the motion of a set point fixed in position relative to a platform that supports the surgeon""s hands and instruments in accordance with said sensed movement so as to maintain a set displacement between said selected and said set points substantially constant.
Broadly the present invention also relates to an apparatus for assisting a surgeon in performing surgery comprising a sensor for sensing the movement of a selected point at or adjacent to a surgical site, a computer, means for providing said sensed movement to said computer, a surgical platform, means of moveably mounting said platform, a set point fixed in position relative to said platform, said computer controlling the movement of said set point fixed relative to said platform in said at least three degrees of movement in accordance with said sensed movement of said selected point to maintain a set displacement between said selected point and said set point substantially constant.
Preferably, said set displacement between said selected point and said set point is selectively defined.
Preferably said method comprises selecting said set point, selecting said selected point, selecting said set displacement and then commencing said controlling the movement of said set point on a platform.
Preferably, said surgical site is on a heart and said controlling comprises determining rhythm and trajectory of point s based on previously sensed historical movement of point s and controlling movement of point p based on said historical movement of point s and correcting said movement of point p based on current sensed movement of point s.
Preferably, said selectively defining comprises a voice control.
Preferably, said selectively defining comprises a joystick control.
Preferably, said selectively defining comprises a foot pedal control.
Preferably a camera system is mounted on and moves with said platform to provide a stabilized view of said surgical site.